''Leptospira'' ( grc, leptos, italics=yes, 'fine, thin' and la, spira, links=no, 'coil') is a genus of
spirochaete
A spirochaete () or spirochete is a member of the phylum Spirochaetota (), (synonym Spirochaetes) which contains distinctive diderm (double-membrane) gram-negative bacteria, most of which have long, helically coiled (corkscrew-shaped or s ...
bacteria, including a small number of
pathogenic and
saprophytic
Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ( ...
species.
''Leptospira'' was first observed in 1907 in
kidney
The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...
tissue slices of a
leptospirosis victim who was described as having died of "
yellow fever
Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains – particularly in the back – and headaches. Symptoms typically improve within five days. ...
".
Taxonomy
''Leptospira'', together with the genera ''Leptonema'' and ''Turneria'', is a member of the family
Leptospiraceae. The genus ''Leptospira'' is divided into 20 species based on DNA hybridization studies.
Pathogenic ''Leptospira''
:''Leptospira alstonii''
Smythe et al. 2013 Haake_et_al._1993.html" ;"title="''Leptospira alstoni''" Haake et al. 1993">''Leptospira alstoni''" Haake et al. 1993:''Leptospira interrogans''
(Stimson 1907) Wenyon 1926 emend. Faine and Stallman 1982 ["''Spirochaeta interrogans''"
Stimson 1907; "''Spirochaeta nodosa''"
Hubener & Reiter 1916; "''Spirochaeta icterohaemorrhagiae''"
Inada et al. 1916; "''Spirochaeta icterogenes''"
Uhlenhuth & Fromme 1916; "''Leptospira icteroides''"
Noguchi 1919]
:''Leptospira kirschneri''
Ramadass et al. 1992
:''Leptospira noguchii''
Yasuda et al. 1987
:''Leptospira alexanderi''
Brenner et al. 1999
:''Leptospira weilii''
Yasuda et al. 1987
:''Leptospira borgpetersenii''
Yasuda et al. 1987
:''Leptospira santarosai''
Yasuda et al. 1987
:''Leptospira kmetyi''
Slack et al. 2009
:''
Leptospira mayottensis
''Leptospira'' ( grc, leptos, italics=yes, 'fine, thin' and la, spira, links=no, 'coil') is a genus of spirochaete bacteria, including a small number of pathogenic and saprophytic species. ''Leptospira'' was first observed in 1907 in kidney t ...
''
Bourhy et al. 2014
Intermediates or opportunistic ''Leptospira''
:''Leptospira inadai''
Yasuda et al. 1987
:''Leptospira fainei''
Perolat et al. 1998
:''Leptospira broomii''
Levett et al. 2006
:''Leptospira licerasiae''
Matthias et al. 2009
:''Leptospira wolffii''
Slack et al. 2008
Non-pathogenic ''Leptospira''
:''Leptospira biflexa''
(Wolbach and Binger 1914) Noguchi 1918 emend. Faine and Stallman 1982 Wolbach_&_Binger_1914.html" ;"title="''Spirochaeta biflexa''" Wolbach & Binger 1914">''Spirochaeta biflexa''" Wolbach & Binger 1914:''Leptospira idonii''
Saito et al. 2013
:''Leptospira meyeri''
Yasuda et al. 1987
:''Leptospira wolbachii''
Yasuda et al. 1987
:''Leptospira vanthielii''
Smythe et al. 2013
:''Leptospira terpstrae''
Smythe et al. 2013
:''Leptospira yanagawae''
Smythe et al. 2013
Members of ''Leptospira'' are also grouped into
serovars according to their antigenic relatedness. There are currently over 200 recognized serovars. A few serovars are found in more than one species of ''Leptospira''.
At its 2002 meeting, the Committee on the Taxonomy of Leptospira of the International Union of Microbiological Societies approved the following nomenclature for serovars of Leptospira. Genus and species names are italicized as usual, with the serovar name not italicized and with an upper case first letter.
:''Genus species'' serovar Serovar_name
For example:
*''Leptospira interrogans'' serovar Australis
*''Leptospira biflexa'' serovar Patoc
Phylogeny
The currently accepted taxonomy is based on the
List of Prokaryotic names with Standing in Nomenclature
List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the nomenclature, naming and Taxonomy (biology), taxonomy of prokaryotes, following the taxonomy requirements and rulings of the In ...
(LPSN) and
National Center for Biotechnology Information
The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The ...
(NCBI).
Morphology
Although over 200 serotypes of ''Leptospira'' have been described, all members of the genus have similar morphology. ''Leptospira'' are spiral-shaped bacteria that are 6-20 μm long and 0.1 μm in diameter with a wavelength of about 0.5 μm.
One or both ends of the spirochete are usually hooked. Because they are so thin, live ''Leptospira'' are best observed by
darkfield microscopy.
The bacteria have a number of degrees of freedom; when ready to proliferate via
binary fission
Binary may refer to:
Science and technology Mathematics
* Binary number, a representation of numbers using only two digits (0 and 1)
* Binary function, a function that takes two arguments
* Binary operation, a mathematical operation that ta ...
, the bacterium noticeably bends in the place of the future split.
Cellular structure
''Leptospira'' have a
Gram-negative
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...
-like cell envelope consisting of a cytoplasmic and
outer membrane. However, the
peptidoglycan
Peptidoglycan or murein is a unique large macromolecule, a polysaccharide, consisting of sugars and amino acids that forms a mesh-like peptidoglycan layer outside the plasma membrane, the rigid cell wall (murein sacculus) characteristic of most ba ...
layer is associated with the cytoplasmic rather than the outer membrane, an arrangement that is unique to
spirochetes
A spirochaete () or spirochete is a member of the phylum Spirochaetota (), (synonym Spirochaetes) which contains distinctive diderm (double-membrane) gram-negative bacteria, most of which have long, helically coiled (corkscrew-shaped or ...
. The two
flagella of ''Leptospira'' extend from the cytoplasmic membrane at the ends of the bacterium into the
periplasmic space
The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the ''periplasmic space'' in gram-negative bacteria. Using cryo-electron microscopy it has been found tha ...
and are necessary for the motility of ''Leptospira''.
The outer membrane contains a variety of
lipoproteins
A lipoprotein is a biochemical assembly whose primary function is to transport hydrophobic lipid (also known as fat) molecules in water, as in blood plasma or other extracellular fluids. They consist of a triglyceride and cholesterol center, su ...
and transmembrane
outer membrane proteins.
As expected, the protein composition of the outer membrane differs when comparing ''Leptospira'' growing in artificial medium with ''Leptospira'' present in an infected animal.
Several leptospiral outer membrane proteins have been shown to attach to the host
extracellular matrix
In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide s ...
and to
factor H. These proteins may be important for
adhesion
Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ( cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another).
The forces that cause adhesion and cohesion can b ...
of ''Leptospira'' to host tissues and in resisting
complement
A complement is something that completes something else.
Complement may refer specifically to:
The arts
* Complement (music), an interval that, when added to another, spans an octave
** Aggregate complementation, the separation of pitch-clas ...
, respectively.
The outer membrane of ''Leptospira'', like those of most other Gram-negative bacteria, contains
lipopolysaccharide
Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer ...
(LPS). Differences in the highly immunogenic LPS structure account for the numerous serovars of ''Leptospira''.
Consequently, immunity is serovar specific; current leptospiral vaccines, which consist of one or several serovars of ''Leptospira'' endemic in the population to be immunized, protect only against the serovars contained in the vaccine preparation. Leptospiral LPS has low endotoxin activity.
An unusual feature of leptospiral LPS is that it activates host cells via
TLR2
Toll-like receptor 2 also known as TLR2 is a protein that in humans is encoded by the ''TLR2'' gene. TLR2 has also been designated as CD282 (cluster of differentiation 282). TLR2 is one of the toll-like receptors and plays a role in the immune sys ...
rather than
TLR4
Toll-like receptor 4 is a protein that in humans is encoded by the ''TLR4'' gene. TLR4 is a transmembrane protein, member of the toll-like receptor family, which belongs to the pattern recognition receptor (PRR) family. Its activation leads to an ...
.
The unique structure of the
lipid A portion of the LPS molecule may account for this observation.
Finally, the LPS
O antigen content of ''L. interrogans'' differs in an acutely infected versus a chronically infected animal.
The role of O antigen changes in the establishment or maintenance of acute or chronic infection, if any, is unknown.
Habitat
''Leptospira'', both pathogenic and saprophytic, can occupy diverse environments, habitats, and life cycles; these bacteria are found throughout the world, except in Antarctica. High humidity and neutral (6.9–7.4) pH are necessary for their survival in the environment, with
stagnant water reservoirs—bogs, shallow lakes, ponds, puddles, etc.—being the natural habitat for the bacteria.
Nutrition
''Leptospira'' are cultivated at 30 °C in Ellinghausen-McCullough-Johnson-Harris (EMJH) medium, which can be supplemented with 0.21% rabbit serum to enhance growth of fastidious strains.
Growth of pathogenic ''Leptospira'' in an artificial nutrient environment such as EMJH becomes noticeable in 4–7 days; growth of saprophytic strains occur within 2–3 days. The minimal growth temperature of pathogenic species is 13–15 °C. Because the minimal growth temperature of the saprophytes is 5–10 °C, the ability of ''Leptospira'' to grow at 13 °C can be used to distinguish saprophytic from pathogenic ''Leptospira'' species.
The optimal pH for growth of ''Leptospira'' is 7.2–7.6.
''Leptospira'' are aerobes whose major carbon and energy source during ''in vitro'' growth is long-chain fatty acids, which are metabolized by beta-oxidation.
Fatty acids are provided in EMJH in the form of
Tween
Preadolescence is a stage of human development following middle childhood and preceding adolescence.New Oxford American Dictionary. 2nd Edition. 2005. Oxford University Press. It commonly ends with the beginning of puberty. Preadolescence is ...
.
Fatty acid molecules are bound by
albumin
Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins ...
in EMJH and are released slowly into the medium to prevent its toxic accumulation.
Like most bacteria, ''Leptospira'' require iron for growth.
''L. interrogans'' and ''L. biflexa'' have the ability to acquire iron in different forms.
A
TonB-dependent receptor required for utilization of the ferrous form of the iron has been identified in ''L. biflexa'', and an
ortholog
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a s ...
of the receptor is encoded in the genome of ''L. interrogans''. ''L. interrogans'' can also obtain iron from
heme
Heme, or haem (pronounced / hi:m/ ), is a precursor to hemoglobin, which is necessary to bind oxygen in the bloodstream. Heme is biosynthesized in both the bone marrow and the liver.
In biochemical terms, heme is a coordination complex "consis ...
, which is bound to most of the iron in the human body. The HbpA hemin-binding protein, which may be involved in the uptake of
hemin
Hemin (haemin; ferric chloride heme) is an iron-containing porphyrin with chlorine that can be formed from a heme group, such as heme B found in the hemoglobin of human blood.
Chemistry
Hemin is protoporphyrin IX containing a ferric iron (Fe3 ...
, has been identified on the surface of ''L. interrogans''
Although other pathogenic species of ''Leptospira'' and ''L. biflexa'' lack HbpA, yet another hemin-binding protein, LipL41, may account for their ability to use hemin as a source of iron.
Although they do not secrete
siderophores
Siderophores (Greek: "iron carrier") are small, high-affinity iron-chelating compounds that are secreted by microorganisms such as bacteria and fungi. They help the organism accumulate iron. Although a widening range of siderophore functions is no ...
, ''L. biflexa'' and ''L. interrogans'' may be capable of obtaining iron from siderophores secreted by other microorganisms.
Genome
The genome of pathogenic ''Leptospira'' consists of two chromosomes. The size of the genomes of ''L. interrogans'' serovars Copenhageni and Lai is approximately 4.6 Mb.
However, the genome of ''L. borgpetersenii'' serovar Hardjo is only 3.9 Mb in size with a large number of pseudogenes, gene fragments, and
insertion sequences Insertion element (also known as an IS, an insertion sequence element, or an IS element) is a short DNA sequence that acts as a simple transposable element. Insertion sequences have two major characteristics: they are small relative to other transp ...
relative to the genomes of ''L. interrogans.''
''L. interrogans'' and ''L. borgpetersenii'' share 2708 genes from which 656 are pathogenic specific genes. The guanine plus cytosine (GC) content is between 35% and 41%.
''L. borgpetersenii'' serovar Hardjo is usually transmitted by direct exposure to infected tissues, whereas ''L. interrogans'' is often acquired from water or soil contaminated by the urine of carrier animals harboring ''Leptospira'' in their kidneys. The high number of defective genes and insertion sequences in ''L. borgpetersenii'' Hardjo together with the poor survival outside of the host and difference in transmission patterns compared to ''L. interrogans'' suggest that ''L. borgpetersenii'' is undergoing insertion-sequence mediated genomic decay, with ongoing loss of genes necessary for survival outside of the host animal.
Genotyping
Genome sequence determination several strains of ''Leptospira'' lead to the development of multilocus
VNTR
A variable number tandem repeat (or VNTR) is a location in a genome where a short nucleotide sequence is organized as a tandem repeat. These can be found on many chromosomes, and often show variations in length (number of repeats) among individ ...
(Variable Number of Tandem Repeats) typing and
multilocus sequence typing
Multilocus sequence typing (MLST) is a technique in molecular biology for the typing of multiple loci, using DNA sequences of internal fragments of multiple housekeeping genes to characterize isolates of microbial species.
The first MLST scheme ...
(MLST) for species level identification of pathogenic ''Leptospira'' species.
Both methods hold the potential to replace the highly ambiguous
serotyping
A serotype or serovar is a distinct variation within a species of bacteria or virus or among immune cells of different individuals. These microorganisms, viruses, or cells are classified together based on their surface antigens, allowing the epi ...
method currently in vogue for leptospiral strain identification.
[
]
See also
* Leptospirosis
* List of bacteria genera This article lists the genera of the bacteria. The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI). However many taxonomic names are ...
* List of bacterial orders
This article lists the orders of the Bacteria. The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI)
and the phylogeny is based on 16S ...
References
External links
''Leptospira'' page at Kenyon College MicrobeWiki.
*
{{Taxonbar, from=Q133841
Spirochaetes
Bacteria genera